Apparatus for producing a cable conduit system suitable for the drawing-in of cables

ABSTRACT

Cable conduit system into which cables of great length, for example waveguide cables, can be drawn, characterized in that a device for the angular deflection of the path of the conduit or cable, in the form of a roller bend, is installed at points where the path of the conduit undergoes a critical change of direction or curvature, this roller bend being connected to the cable conduit in a completely sealed-off manner and support and guide rollers (22, 30) being arranged in various planes in the interior space (20) of this roller bend.

The subject of the present invention is the production of a cableconduit system for the laying of cables, generally buried cables, ofgreat factory length, for example waveguide cables.

As is known, the connecting of two factory lengths possessing waveguidesinvolves a considerable outlay in terms of technology and expenditure.For this reason, efforts are made to keep these connection or splicingpoints to a minimum by manufacturing long lengths of cable, which canamount to 1,000 m or more.

The problem underlying the invention described here consists, then, indrawing such long lengths of cable into a cable conduit system in onepull, and doing so irrespective of the topographical conditions of theterrain in which the cable conduit system is laid and without making useof specialised or heavy equipment.

Experience now shows that coating the drawing element and the interiorsurface of the conduit with a lubricant is not sufficient to overcomethe frictional forces arising, in accordance with the law eμα, in thebends in the conduit, which are sometimes three-dimensional.

The conventional technique for laying cables in trenches makes use ofcable-laying rollers to reduce these frictional resistances,particularly where the path of the cable undergoes a change of directionof a curvature.

The object of the present invention is to apply this technique to thespecial case of drawing cables into the cable conduit described, withthe aim of providing a self-contained, complete and leak-tight pipelinesystem.

In accordance with this object, the invention relates to a method whosedistinctive feature consists in the fact that the devices according tothe invention are installed at points where the run of the cable conduitundergoes critical changes of direction or curvatures. These devices,which are leak-tight themselves, are also connected to the cable conduitin a manner which is tight against dust, water and moisture. Supportrollers and guide rollers are arranged in various planes within theinterior space of these devices.

The effect achieved by the invention is that a cable conduitmanufactured in great lengths (for example 1,000 m), which is deliveredready-to-use to the construction site and is laid, there, canimmediately be used for the drawing-in of cables. This conduit containsthe drawing element necessary for drawing in the cable, and is treatedin a manner such that the slip resistance of the conduit is low and theconduit and drawing elements are protected against corrosion.

One of the possible, non-limited types of embodiment consists, forexample, of a high-density polyethylene pipe with galvanised steel wirelaid therein and, if appropriate, containing lubricant whichsimultaneously imparts to the galvanised steel wire additionalprotection against corrosion.

Clearly, the invention relates to these devices, which are referred toas roller bends in the text which follows. These roller bends representa completely novel commercial article.

For the sake of clarity, an exemplary embodiment is described in thetext which follows, with reference to the attached figures:

FIG. 1: view of an open roller bend;

FIG. 2: view according to the section II--II in FIG. 1;

FIG. 3: view according to the section III--III in FIG. 1;

FIG. 4: side view of a partly open roller bend.

The axial sections of the cable conduits are designated (16) in thefigures.

According to the invention, one or more such roller bends, according tothe example in the drawing, are installed in the cable conduit at pointsof critical changes of direction or curvatures. The roller bend consistsof two-half-shells (10) and (12), as a result of which it is notnecessary to cut the drawing elememt located in the cable conduit wheninstalling the roller bend. The two half-shells are held together byscrews (14). The entrance to and the exit from the roller bend are sodesigned as to be able to accept the ends (16) of the conduit which hasbeen cut at the critical point, and form a leak-tight seal with these bymeans of the gaskets (18).

Guide rollers and support rollers (22) are arranged on spindles (24)within the interior space (20) of the roller bend. The spindles (24) aremounted in the recesses (26) and (28) which are present in thecorresponding half-shells (10) and (12). The rollers (22) are in eachcase located on the inside of the roller bend.

Advantageously, a roller (30) running on a spindle (32) is attachedwithin each half-shell and is aligned perpendicularly to the spindles(24) of the rollers (22).

In this manner effective guidance and easy sliding of the cable (34) areachieved when the latter is drawn in through the roller bend accordingto the invention.

During the drawing-in of the cable, the cable (34) will thus unroll onthe rollers (22) and be additionally guided by the rollers (30),depending on the bend in each case.

The gasket (36) lying in the grooves (38) of each half-shell ensures thesealing-off of the interior space (20) of the roller bend.

If appropriate, projections (40) and fixed centering elements (42) mayalso be provided in the interior space (20) to provide improved anderror-free guiding of the cable to be drawn through the roller bend.

The construction material of the roller bend may be metallic. Moreadvantageously, it is made from corrosion-free, synthetic material.

The degree of deflection of the roller bend can be designed for anychange of direction by the cable conduit.

The device described in the preceding text and the corresponding methodare capable of further development and are to be regarded only as anon-limiting example.

I claim:
 1. An elbow for use in cable conduit systems to facilitate thepulling of cable through such conduits at a point where the conduitmaterially changes direction comprising,a hollow curved body; means forhermetically sealing said body at each end thereof to a cable conduit;and first roller means disposed completely within said hollow body in afirst plane and second roller means spaced from said first roller meansand disposed completely within said body in a second plane for guiding acable therethrough.
 2. An elbow according to claim 1, wherein saidhollow curved body is formed by two shell-like members hermeticallysealed together, whereby the elbow may be inserted in a cable conduitwithout cutting the cable or the means for drawing the cable through theconduit.
 3. An elbow according to claim 2, wherein said first and secondroller means are supported by corresponding recesses within each of saidshell-like members.
 4. An elbow according to claim 1, wherein said firstand second roller means are disposed in planes perpendicular to oneanother.
 5. An elbow according to claim 2, wherein said shell-likemembers are arcuately joined along the line of curvature of said hollowbody.
 6. An elbow according to claim 1, wherein said first roller meanscomprises a pair of opposed rollers each disposed near an inner face ofsaid hollow body and in line with the radius of curvature thereof, andsaid second roller means comprises a roller disposed on each side ofsaid first roller means near an inner curved face of said hollow bodyand perpendicular to said radius.
 7. An elbow according to claim 6,wherein said rollers are cylindrical.